1. Field of the Invention
The present invention generally relates to liquid heating and cooling techniques and, in particular, to a system and method for controlling temperatures of liquids residing within tanks.
2. Related Art
Water tanks are often employed to provide users with heated water, which is drawn from a water tank and usually dispensed from a faucet, showerhead, or like device. During operation, a water tank normally receives unheated water from a water source, such as a water pipe. The water tank includes a controller having a user interface that allows a user to set a desired temperature for the water being held by the tank. If the tank's water temperature falls below the desired temperature, then the controller activates a heating element for warming the tank's water. When activated, the heating element begins to heat the water within the tank, and the heating element continues to heat the water until the water's temperature reaches or exceeds the desired temperature.
The water tank typically does not provide total thermal insulation, and heat from the water often dissipates through the tank and into the surrounding environment. Therefore, over time, the temperature of the water typically decreases. Furthermore, as water is drawn from the tank and used, unheated water from the water source is drawn into the tank to replenish the tank's water supply. This new water is typically at a lower temperature than the heated water within the tank causing the overall temperature of the tank's water to rapidly decrease during times of significant water usage. Due to the foregoing factors that tend to reduce the tank's water temperature, activation of the heating element is frequently required to maintain the temperature of the water at or close to the desired temperature. Moreover, activation of the heating element can be particularly frequent and/or long during times of high water usage and for water tanks providing poor thermal insulation.
Activation of the heating element typically requires electrical power. In this regard, a heating element is normally comprised of one or more resistive elements that emit heat when electrical current is passed through the heating element. As a result, the operational costs associated with a water heater are directly related to the amount of heat generated by the heating element. More specifically, any increase in the amount of heat generated by the heating element normally increases the energy costs and, therefore, the overall operational costs associated with the water heater. Indeed, many consumers utilize a tank's energy efficiency as a primary factor when purchasing a water tank. Thus, there exists a need in the art for more efficient water tanks that operate with lower energy costs.
Another problem with conventional water tanks pertains to failure of the heating element. For the reasons set forth above, a heating element within a water tank may be frequently activated and deactivated in an attempt to maintain the tank's water temperature at the desired level. Over time, the frequent transitions of the heating element increase the wear experienced by the heating element, and the heating element eventually fails. When the heating element fails, a user can either replace the water tank entirely or fix the water tank by replacing the failed heating element. However, during the time that it takes to fix or replace the water tank, the water tank often fails to maintain the water temperature at the desired level. In most situations, a user has no alternative source for heated water and, therefore, is not able to keep water at the desired temperature until the water tank is either fixed or replaced. This can be very inconvenient for the user, and the longer that it takes to fix or replace the water tank, the more the user is inconvenienced.
Some water tanks referred to as “water coolers,” have cooling elements instead of heating elements in order to keep the water within the tanks at or below a desired temperature. Such tanks commonly hold drinking water that can be dispensed through a faucet, fountain, nozzle or other type of water dispensing device. In order to keep the water within a particular tank at or below the desired temperature, the cooling element is activated when it is detected that the water temperature has risen above the desired temperature. The cooling element cools the water within the tank until the water temperature falls below the desired temperature. Like the heating element, electrical power is typically required to activate the cooling element. Thus, the operational costs associated with a water cooler are directly related to the amount of cooling performed by the cooling element. More specifically, any increase in the amount of cooling performed by the cooling element normally increases the energy costs and, therefore, the overall operational costs associated with the water cooler.